If this is your first visit, be sure to
check out the FAQ by clicking the
link above. You may have to register
before you can post: click the register link above to proceed. To start viewing messages,
select the forum that you want to visit from the selection below.

transportation of dry cement powder

For my thesis I am dealing with dense phase transportation of powder and I would like to have an overview about the turbulences and segregation inside a pipe at dense phase transport of dry cement powder.
For transportation velocities of about 10 meters per second (about 30 ft per second) a volume ratio of 30% dry powder to 70% of air occurs in a 7 centimeter (2.8 inch) pipe.

Seeing the pipe in cross-section, particles of the inner "layers" move faster than particles of outer layers.
My question now is: Are particles, located in an outer layer inside the pipe, a few feet later in the pipe still located in an outer radius or are they now at a totally different position? In other words, if I would mark powdery particles in different positions of the pipe's cross-section, are they still at the same (similar) position in the cross-section a little bit later in the pipe?

Are there any formulas (maybe related to formulas in the hydrodynamics??), models or software solutions to simulate the dense phase flow of the powder at different conditions?

Is there any database (or knowledge) available about the properties of dry cement powder and the flow properties of the powder in a pipe (friction, flow function, stress,...)?

Anton
It is probably best to try and think of what force there might be holding a particle in a particular position relative to other particles.
I can think of none, however I can think of many (including gravity & turbulence ) that will want to move it out of a linear path.
Regards

Segregation in dense phase conveying

Generally, transverse segregation across a pnuematic conveying pipe is of little interest, if indeed it occurs, because the material emerging is delivered together into a receiving vessel at relatively high velocity where segregation is much more dependent upon the disengagement process.

Logitudinal segregation along the pipe run is related to the viscus drag of the individual particles, impeded by the formation of plugs, dunes and other mechanical interferences of the particulate structure. In essence, the results bear on the starting and stopping conditions, rather than the main run where lagging and leading particle fractions are attenuated by linear compensation. With respect to cement, it is unlikely that significant segregation will occur in the pipeline run, other than a smattering of dust separating from the main mass.